In 1991 Fisher & Paykel Limited released the first model of their SMARTDRIVE washing machines. This machine included a cabinet, a tub suspended within the cabinet by a plurality of suspension rods extending between the top edge of the cabinet and a lower portion on the tub. A single shaft extended through the base of the tub. The stator of a salient pole electronically commutated brushless DC motor was fixed to the lower side of the tub base. An external permanent magnetic rotor was fitted to the lower end of the shaft to substantially surround the stator. Within the tub a spin basket was supported for rotation on the shaft. Within the spin basket an agitator was fixed to the upper end of the shaft. The agitator was of a central post type with three lateral vanes and a generally conical base portion. The spin basket was supported by the shaft at a lower position, and was free to rise on the shaft to an upper position. The spin basket included downwardly facing hollow chambers. Vertical support of the spin basket on the shaft in the lower position included inter-engagement of a downwardly facing castellated clutch on the spin basket and an upwardly facing castellated clutch fixed to the shaft. Accordingly, without sufficient wash liquid in the tub for the spin basket and any associated load to float, the spin basket remained rotationally fixed to the shaft. With sufficient wash liquid in the tub, the float chambers of the spin basket would provide for the basket and load to float and disengage from the shaft, such that the shaft would rotate independently of the spin basket. This arrangement is described in U.S. Pat. No. 5,353,613. This direct drive electronically controlled laundry machine has been very successful. A number of competing companies have sought to devise alternative arrangements for selectively transmitting power of the motor to the spin basket.
U.S. Pat. No. 6,212,722 proposes an improved laundry washing machine for domestic use. This machine is of the top loading type having an outer bowl, a wash basket within the outer bowl and access to the wash basket through a top opening. A motor is provided to drive rotation of the wash basket within the outer bowl. A wash plate is provided in the lower portion of the wash basket to be rotated by the motor with the wash basket or independently of the wash basket. The patent proposes a combination of water level control, wash plate design, wash basket design and movement pattern for the wash plate which leads to an inverse toroidal movement of the laundry load during a wash phase. The sodden wash load is dragged radially inward on the upper surface of the wash plate and progresses upward in the region of the centre. The sodden wash load then progresses radially outward to the wall of the wash basket and downward to the base of the wash basket. This has been found to provide an effective wash action with low water consumption.
When a wash system of the type disclosed in U.S. Pat. No. 6,212,722 is applied to a machine of the type described in U.S. Pat. No. 5,353,613, the water volume required to operate the floating clutch can be a significant factor in overall water consumption.
In order to selectively couple the spin basket to the drive, the applicant has applied lost motion clutch arrangements to uncouple the spin basket for a range of motion. In WO 2007/114712, a laundry machine comprises a lost motion clutch located in the tub. The lost motion clutch interconnects between the drive assembly and the spin basket and absorbs greater than one revolution of relative rotation, to allow the agitator to move independently of the spin basket. In WO 2008/143528, a laundry machine comprises a lost motion clutch engaged between the drive assembly and the spin basket to allow the agitator to move independently of the spin basket. The lost motion clutch absorbs greater than one revolution of relative rotation between the agitator and the spin basket. The amount of uncoupling provided by a lost motion clutch is limited by the range of travel between the end conditions of the clutch.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.
It is an object of the present invention to provide an improved clutch for a laundry appliance, or to at least provide the industry with a useful choice.